Skyrmion Hall Effect Revealed by Direct Time-Resolved X-Ray Microscopy

TL;DR

This study uses advanced X-ray microscopy to directly observe the real-time dynamics of current-driven magnetic skyrmions, revealing a linear increase in the skyrmion Hall angle with velocity, challenging existing theories.

Contribution

First direct nanoscale imaging of skyrmion dynamics under current-induced spin orbit torque, showing a linear velocity dependence of the skyrmion Hall angle.

Findings

Skyrmions move at an angle exceeding 30° relative to current.

The skyrmion Hall angle increases linearly with velocity up to 100 m/s.

Internal mode excitations and field-like SOT influence skyrmion dynamics.

Abstract

Magnetic skyrmions are highly promising candidates for future spintronic applications such as skyrmion racetrack memories and logic devices. They exhibit exotic and complex dynamics governed by topology and are less influenced by defects, such as edge roughness, than conventionally used domain walls. In particular, their finite topological charge leads to a predicted "skyrmion Hall effect", in which current-driven skyrmions acquire a transverse velocity component analogous to charged particles in the conventional Hall effect. Here, we present nanoscale pump-probe imaging that for the first time reveals the real-time dynamics of skyrmions driven by current-induced spin orbit torque (SOT). We find that skyrmions move at a well-defined angle {\Theta}_{SH} that can exceed 30{\deg} with respect to the current flow, but in contrast to theoretical expectations, {\Theta}_{SH} increases linearly with velocity up to at least 100 m/s. We explain our observation based on internal mode excitations in combination with a field-like SOT, showing that one must go beyond the usual rigid skyrmion description to unravel the dynamics.